This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cytokinesis is the process that completes cell division, physically partitioning the mother cell into the two daughter cells. In animal cells, cytokinesis is accomplished by constriction of a cortical contractile ring. Contractile rings are composed of a network of protein polymers that includes actin filaments, bipolar filaments of the motor myosin II, and septin filaments. Contractile rings also contain the crosslinker anillin, which binds directly to all three filament types, and proteins that regulate actin nucleation, capping, polymerization, disassembly, and crosslinking. Although we already know many of the contractile ring components, much is still to be learned about the molecular architecture of this structure. We are trying to build a molecular network that allows constriction to happen by looking for interactons among known ring components by mass-spectrometry.